Iran warns unexploded US bunker-buster bombs are still inside nuclear facilities hit in 2025.

Iranian Foreign Minister Abbas Araghchi said unexploded munitions remain at nuclear facilities struck by the United States in June 2025, creating safety risks for inspections, and these weapons could potentially include GBU-57 Massive Ordnance Penetrator bombs.

As reported by the Middle East Monitor on February 8, 2026, Iran stated that unexploded bombs remain at nuclear facilities hit by US strikes in June 2025 and cited them as a physical hazard preventing inspections. Foreign Minister Abbas Araghchi said inspections can only proceed after agreement on safety, security, and access protocols, noting that no existing international rules address inspections at bombed nuclear sites, especially as the U.S. used a total of fourteen GBU-57A/B MOP bunker-buster bombs.
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If unexploded GBU-57 bombs are recovered after removal or neutralization, they could provide Iran with direct access to a modern bunker-penetrating weapon, potentially allowing the measurement of casing thickness and alloy composition. (Picture source: US DoD)

Iran stated that unexploded bombs remain present at nuclear facilities struck by the United States in June 2025, and said this situation creates concrete safety and security obstacles to any inspection activity. Foreign Minister Abbas Araghchi said the presence of unexploded munitions represents a physical hazard at sites that were bombed during the conflict. He stated that there is no existing legal framework or protocol governing visits to nuclear facilities that have been attacked. According to him, this absence of rules makes the situation unprecedented. Iran is therefore requesting that a specific protocol be agreed upon before any visit takes place. These remarks were made while Iran remains in contact with the International Atomic Energy Agency.

Araghchi said he asked the IAEA Director General whether any law or formal procedure exists for visits to nuclear facilities targeted by US strikes, and said the response was that none exists. He stated that Iran informed the agency that inspections should only occur after agreement on safety and security issues. He explicitly cited unexploded bombs as one of the unresolved hazards that must be addressed in advance. He added that other technical and access-related matters would also need agreement before inspections. Araghchi said Iran remains in contact with the agency on this issue. He also reiterated that Iran does not trust the United States and described the outcome of ongoing Iran–US talks as uncertain.

The nuclear strikes occurred during a 12-day conflict in June 2025, which Iran describes as an assault launched by Israel with US support. According to Iranian officials, the campaign targeted military installations, nuclear facilities, and civilian infrastructure across the country. They also stated that the conflict included assassinations of Iranian military commanders and nuclear scientists. Iran responded during the conflict by launching missile and drone attacks against Israeli military and intelligence targets. The confrontation marked a period of direct military exchanges between the two sides. Iranian officials have consistently treated the nuclear strikes as part of this broader campaign.

During the same conflict, the United States conducted strikes against three Iranian nuclear sites before announcing a ceasefire. The sites struck were Fordow, Natanz, and Isfahan, which are central to Iran’s uranium enrichment and nuclear technology activities. Iranian officials later acknowledged that these facilities sustained significant damage. They also stated that nuclear material had been relocated prior to the strikes and that there was no immediate radiological threat to nearby populations. The ceasefire ended active hostilities but left damaged structures and unexploded ordnance at the affected sites. Iran now cites these conditions as continuing constraints on access.

The US strikes involved the use of heavy GBU-57 Massive Ordnance Penetrator (GBU-57 MOP) bunker-buster bombs delivered by B-2 strategic bombers, each weighing roughly 13,600 kg and designed to penetrate deep layers of rock and reinforced concrete before detonation. In addition, Tomahawk cruise missiles were used against nuclear-related infrastructure. The GBU-57 Massive Ordnance Penetrator is a U.S. bunker-buster bomb that has a length of roughly 6.2 meters and a hardened steel casing designed to withstand high-speed impact. It is guided by a combined GPS and inertial navigation system and uses a delayed fuze to detonate after penetrating rock or reinforced concrete. Delivery is limited to B-2 strategic bombers due to the weapon’s size and weight.

During the operation Midnight Hammer, multiple GBU-57 bombs were employed against underground nuclear facilities, including sites built under significant overburden. The intent was to damage underground halls, access tunnels, and critical internal infrastructure rather than surface buildings. The bomb’s penetration capability is based on kinetic energy and casing strength rather than blast alone. Estimates commonly cited for the GBU-57 indicate penetration of several tens of meters of earth or many meters of reinforced concrete, depending on material density and angle of impact. The fuze can be programmed to delay detonation until the weapon reaches a specific depth, increasing damage to underground structures. In the Iran strikes, some bombs were reportedly aimed at ventilation shafts and access points to maximize internal effects. If a fuze fails to trigger or is disrupted by impact conditions, the bomb may not detonate. In such cases, a largely intact munition can remain embedded underground or within collapsed structures.

If unexploded GBU-57 bombs are recovered after removal or neutralization, they could provide Iran with direct access to a modern bunker-penetrating weapon for technical examination. Physical inspection could allow measurement of casing thickness, alloy composition, and structural reinforcement intended to prevent fracture during penetration. Internal components such as guidance electronics, power systems, and navigation sensors could also be examined if not destroyed on impact. Analysis of the fuze assembly could reveal how detonation timing and depth sensing are implemented. Such information would be relevant for understanding penetration mechanics and the survivability of the weapon. Recovery would not imply reuse, as safe handling would require complete neutralization of the explosive content.

Potential reverse engineering would face substantial technical limits even with recovered hardware. The GBU-57 depends on specialized high-strength steel alloys, precision machining, controlled explosives, and extensive testing under extreme conditions. Replicating similar penetration performance would require comparable industrial capacity and access to large-scale forging, metallurgy, and validation facilities. Integration would also require a delivery system capable of carrying a payload exceeding 13 tonnes, which significantly narrows practical options. More realistically, examination of recovered bombs could inform defensive measures, such as adjusting tunnel depth, layout, or reinforcement to reduce vulnerability. Iran has not stated that it is pursuing replication, and recovery alone does not equate to operational capability.

Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.